2. Gears
A gear is a wheel with teeth on its outer edge.
The teeth of one gear mesh (or engage) with the teeth of another.
Above
Gears meshing or engaged
3. Gears
Driver and Driven
• Two meshed gears always
rotate in opposite directions.
Driver gear
Driven gear
Spur Gears
5. Gears
• Multiple gears can be connected together to form a gear train.
Simple Gear Train
Each shaft carries only
one gear wheel.
Intermediate gears are
known as Idler Gears.
7. Gears
• Generally, the Gear Ratio is
calculated by counting the teeth of
the two gears, and applying the
following formula:
Gear ratio = Number of teeth on driven gear
Number of teeth on driver gear
Gear Ratio
8. Gears
Gear Ratio - Calculation
A 100 tooth gear drives a 25
tooth gear. Calculate the gear
ratio for the meshing teeth.
Gear ratio = Number of teeth on driven gear
Number of teeth on driver gear
Gear ratio = driven 25 = 1
driver 100 4
This is written as 1:4
9. Gears
Gear Speed :- Calculation
A motor gear has 28 teeth
and revolves at 100 rev/min.
The driven gear has 10 teeth.
What is its rotational speed?
Speed of driven gear = Number of teeth on driver gear x 100
Number of teeth on driven gear
Speed of driven gear = driver = 28 x 100 = 280 rev/min
driven 10
28 teeth,
driver
10 teeth,
driven
10. Gears
• The worm gear is always
the drive gear
Worm and wheel
Worm gear and wheel
11. Gears
• The rack and pinion
gear is used to convert
between rotary and
linear motion.
Rack and Pinion
Heavy Duty
Car Jack
12. Gears
• Bevel gears are used to transfer drive through an
angle of 90o.
Bevel Gears
Bevel gears
13. Important Calculations : -
Work Done = Force x Distance moved in the direction of the force
Power =
Total Time Taken
Total Work Done
Efficiency % =
Power Output
Power Input
Friction: - Resists the movement of one surface over another
X 100
Efficiency = Mechanical advantage
Velocity ratio
